Electric motor control



9 R949 R. B. HUNTER ELECTRIC MOTOR CONTROL Filed May 16, 1946 "will Patented Dec. 27, 1949 UNITE-D s TATiEiS iflFfFICE R cha 13- Hunter, as psl, Wis, aa i o 40 Cutler-Hamm er, 1110., Milwaukee, Wis a cor- .poration. of Delaware Application May 16, 1946,"Serial'No.= 670,'064

9 Claims. (0]. 318-305) .This invention relates to improvements in electric motor control. Although ;not limited thereto, the inventionv is particularly adapted for con..- trol of the driving motor of a dough .mixing machine.

In a dough mixing .machinetof ;the character herein contemplated :there :are .two operating 'positions, :namely, the ..mixing position and :the dumping position. The control :system includes alimit switchwhichis automatically:closed-wvhen the parts .are in .mixing position, and :opened when the ,parts are in dumping position. llhe parts -.of the imachine, .of course, include 'a containerior the.do.ugh andlalmotor driven element within the container for :efiecting :mixing of the dough.

I :have illustrated .the invention as applied to the control .of an alternating current driving motor .having primary windings vto vbe selectively connected in circuit .to provide for either-slow speed operation or fast speed operation :of :the motor. The control system includes an electromagnetic -contactor adapted when :energized to complete -a circuit ifor slow speed operation of the motor; energization of :said contaetor being subject to control by a special form of mushbutton switch having upper and lower ibridging members; -.the -upper bridging member #being first engaged .with its associated contacts but being ineffective to :complete :the energizing circuit pending engagement of the lower bridging -m'ember with its associated contacts. Conversely, upon partial release-0f said .pushbutton, such as to :provide for disengagementof the lower bridging member the energizing circuit of the slow speedzcontactor will be maintained pending full release :of the pushbutton, with consequent disengagementof the upper bridging member from its contacts. This arrangement prevents rapid tickling of the slow speed contactor, thereby avoiding rapid deterioration -of the main contacts thereof.

1 Moreover, it is desirable that "the motor shall not be operable at fast speed until it has first been operated 'at slow speed by operation o'fthe aforementioned pushbutton. It is also desirable that, after the motor has been connected .for operation thereof at fast speed, the motor will not'be transferred back to slow speed by,merel y releasin the fast speed pushbutton, even-though the slow speed pushbutton switch may have been manually held in fully closed position. ;By this means breaking of driving chains or gearing (due to .a rapid change from .fastaspeed :toslow 2 speed of the :driving motor) is effectively prevented.

It is further desirable that during the mixing operation the motor :may be operated continuously at either slow :speed 1or=fast speed without requiring manual retention of either the slow speed pushbutton or the fast speed :pushbutton in depressed position; :whereas when the dough mixing apparatus is in the dump position :it is preferred=that the driving motor willibe ioperated only g-during manual depression of either the slow speed vpusl'ibutton, or .of both pushbuttons; the arrangement being 'suchthat =by momentary closure ;of the 'fast speed *pushbutton during :main.- tenance of the slow speed pushbutton in .atleast partially Idepressed position athe fast speed relay and the fast speed contactor may :be energized and thereafter maintained energized 'by .such partial depression of .said slow speed :pushbutton.

My invention hasamongtits objects to provide for'attainmentof allof the aforementioned desirable results.

Other objects and advantages of my invention will hereinafter appear.

IPhe accompanying drawing, consisting of a single figure, illustrates schematically .and diagrammatically a preferred formof electric'm'otor control embodying my invention.

In the drawing, the :reference character 3M designates 'ingeneral a 1motor, th'e rotatable .armature :m :of which (may be :assumed'to have a positive vdriving :connection #with the rotatable paddles or agitators, shown in dotted 1ines:at E, of adough :mixing machine D. The primary of motor M consists ofssix windings-sections, designated :by the .numerals -l to 6, inclusive; said sections being connected end to :end in series relationship to each other and forming a closed circuit. Terminals T \T -arId T iare electrically connected to said sections at points between the respective :pairs II ,22; -3, :4, and 5, 6, as illustrated. Terminals-Tl, T -and T are respectively-adapted to beconnected to lines 1 L and :L of-asuitable source :of alternating current supply. upon closure-of the -normally open main contacts sl, S and S v.of a slow speed contaotor S; the electromagnetic closing winding of which is designated Joy-reference character S Contactor S is provided with normally closed auxiliary contacts S and normally .open auxiliary icontacts rSi.

Motor Mmaygbe connected to:.lines L Lland L for fast speed operation thereof 'byeclosure of a fast speed contactor the same having a group of three ;normally open main contacts .F

F and F a pair of additional normally open main contacts F and F and normally closed auxiliary contacts F The operating winding of contactor F is designated by reference character F Energization of the operating winding F" of contactor F is dependent upon prior closure of the normally closed auxiliary contacts S of contactor S. Deenergization of the operating winding S of contactor S for this purpose is insured by the provision of fast speed relay FR, having normally closed contacts FR normally open contacts FR and an operating winding PR As aforestated, however, the control means hereinafter described are adapted to normally function in a manner to insure against closure of the main contacts of fast speed contactor F prior to closure and reopening of the main contacts of slow speed contactor S.

Upon energization of the winding F of contactor F the main contacts F F and F will close to provide for connection of lines L L and L to the motor terminals T T and T respectively. Main contacts F and F will be simultaneously closed to provide a common point of connection at X between the respective motor terminals T T and T The control means for contactors F and S and relay FR comprise a special form of pushbutton switch 1, designated by the legend Slow; a second pushbutton switch 8, designated by the legend Stop; and a third pushbutton switch 9, designated by the legend Fast. Pushbutton I is provided with a spaced pair of bridging members l and l which are normally disengaged from their cooperating sets of stationary contacts l and i respectively. The arrangement is such that upon depression of pushbutton 1 the member i will first engage its cooperating contacts 7, but nothing is energized until the member l engages its associated contacts 7 a suitable mechanical connection being provided between members I and l for this purpose; as indicated by the dotted line 1 The arrangement is also such that upon manual release of pushbutton 'd the bridging member l will first disengage contacts 1 and thereafter the bridging member t will disengage contacts 1. The Stop pushbutton 8 is provided with normally closed contacts 8 and the Fast pushbutton 9 is provideed with normally open contacts 9 Upon full manual depression of pushbutton 1 in the manner aforedescribed, a circuit is completed for the operating winding S of slow speed contactor S; said circuit extending from line L by conductor l through the contacts 8 of the normally closed pushbutton switch 8, by conductors II and [2 through the contacts I of pushbutton switch I (which contacts are then bridged by member W), by conductors l3 and I 4 through the normally closed auxiliary contacts F of contactor F, by conductor 15 through the normally closed auxiliary contacts PR of relay FR, by conductor 16 through the operating winding S of contactor S, and by conductor ll to line L The normally open main con tacts S S and S are thus closed to complete the aforementioned circuit for slow speed operation of motor M. At the same time the normally closed auxiliary contacts S of contactor S are opened, to insure against simultaneous energization of the operating Winding F" of contactor F. Moreover, the normally open auxiliary contacts S of contactor S are closed to provide a circuit shunting the lower bridging member l and its associated contacts I That is to say, upon partial manual release of pushbutton 1 (so that member 1 is disengaged from contacts 1 while member 7 is held in engagement with contacts 1), the energizing circuit for winding S will extend from line L to and through conductor [2, as aforedescribed, and thence by conductor i8 through contacts 1 (then bridged by member 1 by conductors I 9 and 20 through said auxiliary contacts S and thence by conductor 2| through conductor M to line L in the manner aforementioned.

If the dough mixing machine is in the mixing position, the limit switch LS will be closed as shown, and therefore a maintaining circuit will be provided for operating winding S entirely independently of pushbutton switch 1; so that the latter may be entirely released manually. Said maintaining circuit may be traced from line L by conductor :0 through the normally closed contacts 8 of switch 8, by conductors H and 22 through the limit switch LS, by conductor 23 to and through conductor 20, and thence, as heretofore traced, through winding S to line L If the dough mixing machine should be in dumping position at the time winding S is energized by complete manual depression of pushbutton switch I, the limit switch LS will be opened; and, accordingly, although the energizing circuit of winding S can be maintained by manual retention of pushbutton I depressed to an extent sufiicient to afford engagement of member "F with contacts 1, it will be apparent that upon full manual release of pushbutton 7 said energizing circuit Will be interrupted, with consequent stopping of motor M.

If it is desired to stop motor M when operating at slow speed durin the mixing operation it is only necessary to momentarily depress the pushbutton 8, thus interrupting the aforedescribed maintaining circuit, for operating winding 8* of contactor S, which extends through the limit switch LS. Under such conditions the pushbutton 7 should previously have been at least partially released manually (to provide for disengagement of member l from contacts i to avoid restarting of motor M at slow speed upon manual release of pushbutton 8. On the other hand during operation of motor M at slow speed for dumping, said motor may be stopped at will by merely completely manually releasing pushbutton l; inasmuch as limit switch LS will then be in open position.

If, during operation of motor M at slow speed for mixing the dough, it is desired to operate motor M at fast speed, it is only necessary to effect manual closure of pushbutton switch 9. This first completes an energizing circuit for the operating winding PR of relay FR; which circuit may be traced from line L by conductor 10 through normally closed pushbutton switch 8, by conductors ii and 22 through limit switch LS, by conductors 23 and through the auxiliary contacts S of contactor S, by conductors 2| and 24 through the contacts 9 of pushbutton switch 9, by conductor 25 through said winding FR and by conductors 26 and i? to line L Upon closure of the normally open contacts FR of relay FR a maintaining circuit is completed for the winding PR said circuit extending from line L through pushbutton switch 8 and limit switch LS, thence by conductors Z3 and 21 through said contacts FR and by conductors 28 and 25 through winding PR to line L as heretofore traced. Upon opening of the es ap contacts :5 of contactor S, andby conductor 30 through windin F and conductor H to line L1.

"With'windings FR and? thus energized, during operation of motor M at fast speed for mixing, :theienergizing circuit for the former willibe maintained through pushbutton switch 8, limit I switch LS and contacts PR and the energizing circuit for the latter will be maintained by the samelmeans, plus the normally closed contacts 5 11f contactor S; said maintaining circuits, of -course, being independent of the pushbutton switchi9, which may therefore be manually released. Such fast speed operation of motor M will be continued pending momentary deprestion of the Stop pushbutton switch 8, as will be obvious.

On'the other hand, if the dough mixing -ma chine is moved (manually or otherwise) to the dumping position thereof shown in dotted lines limit switch LS will be opened, as indicated by dotted "lines, and hence the fast speed operation of motor M will be discontinued immediately, @unless at the time the contacts i 1 of pushbutton switch I are manually held in engagement. Complete manual release of pushbutton switch "I 'under such conditions will, of course, effect interruption of the motor circuit.

'While I have herein shown the motor M as being o'f-the three phase, single winding, constant torque type, it is to be understood that ,a three phase, single winding, variable torque type motor might be substituted therefor, if desired. .Moreover, it is obvious that various other types -.of motors, having alternative circuit connections to provide for slow speed or fast speed operation thereof might be employed.

It "is to be understood that the paddles 'P are always rotated in the same direction, as indicated by the dotted line arrow ,Z, so that upon movement of the machine D :to dumping position said paddles will act to kick the finished dough out .of the machine into acart Y or other suitable form .of container, whereby ,the same may be conveyed to the desired point of use.

"I claim:

1. In .a control system for a motor having a slow speed connection and a fast speed connection, a ,slow speed contactor adapted when closed by energization of the operating coil thereof to complete said slow speed motor connection, a fast speed :contactor .adapted when closed 'to complete said fast speed motor connection, a slow speed pushbutton switch having two normally open sets of contacts, one set of contacts being adapted when initially closed to energize said operating coil of said slow speed contacton-the other set of contacts being adapted when closed -to provide an alternative energizing circuit for said coil in series with a normally open auxiliary interlock on said slow speed contactor,

a normally open fast speed pushbutton switch, means including a relay having normally :closed and normally .open contacts respectively effective upon closure of said fast speed pushbutton switch after closure of said s'low.sp.eed,pushbutton switch to deenergize the operating coil of saidslow speed contactor and-toenergize theopcrating coil :of said fast speed contactor, and said normally open contacts of said :relay when closed providing .a maintaining circuit for "said fast speed contactor in series with the second mentioned contactson saidzslow speed pushbutton switch, whereby the operating coil of said fast speed contactor will be deenergized under .given conditions only after complete manual release .of said slow speed pushbutton switch.

2. :In a control system for a motor having a slow speed connection and a fast speed connection, aslow speed contactor adapted when closed by energization of the operating coil thereof to complete said slow speed motor connection, .a fast speedcontactor adapted when closed to com-.- plete said fast speed :motor connection, a slow speed pushbutton switch :having two normally 'open sets of contacts, one set of contacts being adapted when initially closed to energize rsaid operating coil of said slow speed contactor,'the other set of contacts being adapted when closed to provide an alternative energizing circuit for said coil in series with a normally open auxiliary interlock on said slow speed contactor, a normally open fast speed pushbutton switch, means including a relay effective upon closure of said fast speed pushbutton switch after closure of said slow speed pushbutton switch to deenergize the operating coil of said slow'speed contactor'and to energize the operating coil of said fast speed contactor, said relay havin normally open contacts adapted when closed to provide a maintaining circuit for said fast speed contactor in series with the second mentioned contacts on said slow speed pushbutton switch, the operating .coil of said relay being subject to energization control by said slow speed and fast speed pushbutton switches jointly, the arrangement Joeing such that the operating coil of said fast speed contactor will be deenergized under given conditions only after complete manual release of .said .slow speed pushbutton switch, and means including a limit switch arranged in .parallel with .said second .mentioned contacts on said slow speed pushbutton switch, said limit switch when closed being adapted to maintain the en.- ergizing circuit of either the slow speed or .fast speed contactor independently of both the slow speed and fast speed pushbutton switches.

3. In a control system for a motor having a slow speed connection and a fast speed connection, a slow speed contactor adapted when closed by energization of the operating coil-thereof "to complete said slow speed motor connection, a fast speed contactor adapted when closed to complete said fast speed motor connection, a slow speed pushbutton. switch having two normally open sets of contacts, one of said sets of-contacts being adapted when initially closed to energize said operating coil of said slow speed contactor, the other of said sets of contacts being adapted when closed to provide an alternative energizing circuit for said coil in series with a normally open auxiliary interlock on said slow speed contactor, a normally open fast speed pushbutton switch, means including a relay effective upon closure of said fast speed pushbutton switch after complete closure of said slow speed pushbutton switch to deenergize the operating coil of said slow speed contactor and to energize the operating coil -of said fast speed contactor, said relay having normally open contacts adapted when closed to provide a maintaining circuit for .said fast speed contactor in series with the second mentioned contacts on said slow speed pushbutton switch, and means to cause said second mentioned contacts on said slow speed pushbutton switch to break circuit only after said first mentioned contacts thereon have broken circuit, whereby complete manual release of said slow speed pushbutton switch is required to effect interruption of said maintaining circuit.

4. In a control system for a motor having a slow speed connection and a fast speed connection, a slow speed contactor adapted when closed by energization of the operating coil thereof to complete said slow speed motor connection, a fast speed contactor adapted when closed to complete said fast speed motor connection, a slow speed pushbutton switch having two normally open sets of contacts, one set of contacts being adapted when initially closed to energize said operating coil of said slow speed contactor, the other set of contacts being adapted when closed to provide an alternative energizing circuit for said coil in series with a normally open auxiliary interlock on said slow speed contactor, a normally open fast speed pushbutton switch, means including a relay effective upon closure of said fast speed pushbutton switch after complete closure of said slow speed pushbutton switch to deenergize the operating coil of said slow speed contactor and to energize the operating coil of said fast speed contactor, said relay having normally open contacts adapted when closed to provide a maintaining circuit for said fast speed contactor in series with the second mentioned contacts on said slow speed pushbutton switch, means to cause said second mentioned contacts on said slow speed pushbutton switch to break circuit only after said first mentioned contacts thereon have broken circuit, whereby complete manual release of said slow speed pushbutton switch is required to effect interruption of said maintaining circuit, and means including a limit switch adapted to be closed under given conditions, said limit switch when closed being adapted to render the slow speed pushbutton switch incapable of interrupting said maintaining circuit.

5. In a control system for a motor having a slow speed connection and a fast speed connection, a slow speed contactor adapted when closed by energization of the operating coil thereof to complete said slow speed motor connection, a fast speed contactor adapted when closed to complete said fast speed motor connection, a slow speed pushbutton switch having two normally open sets of contacts, one set of contacts being adapted when initially closed to energiz said operating coil of said slow speed contactor, the other set of contacts being adapted when closed to provide an alternative energizing circuit for said coil in series with a normally open auxiliary interlock on said slow speed contactor, a normally open fast speed pushbutton switch, means including a relay efiective upon closure of said fast speed pushbutton switch after complete closure of said slow speed pushbutton switch to deenergize the operating coil of said slow speed contactor and to energize the operating coil of said fast speed contactor, said relay having normally open contacts adapted when closed to provide a maintaining circuit for said fast speed contactor in series with the second mentioned contacts on said slow speed pushbutton switch, means to cause said second mentioned contacts on said slow speed pushbutton switch to break circuit only after said first mentioned contacts thereon have broken circuit, whereby complete manual release of said slow speed pushbutton switch is required to effect interruption of said maintaining circuit, means including a limit switch adapted to be closed under given conditions, said limit switch when closed being adapted to render said slow speed pushbutton switch incapable of interrupting said maintaining circuit, and a third pushbutton switch having normally closed contacts, said last mentioned contacts when opened bein adapted to insure deenergization of the slow speed and fast speed contactors.

6. In a control system for the driving motor of a dough mixing machine or the like having an upright mixing position and a tilted dumping position, wherein operation of the motor at either a slow speed or a fast speed under both mixing and dumping conditions is required, in combination, a slow speed contactor having an operating coil adapted when energized to provide for slow speed operation of said motor, a fast speed contactor having an operating coil adapted when energized to provide for fast speed operation of said motor, a slow speed pushbutton switch having two normally open sets of contacts one of which sets is adapted when initially closed to energize the operating coil of said slow speed contactor, the other set of contacts of said switch being adapted when closed to provide an alternative energizing circuit for said coil in series with a normally open interlock on said slow speed contactor, a fast speed pushbutton switch having a normally open set of contacts adapted upon closure thereof, but only after closure of both sets of contacts of said slow speed pushbutton switch, to effect operating energization of said fast speed contactor, means including a limit switch which is closed when said machine is in its upright position, whereby upon temporary closure of said slow speed pushbutton switch, or of said slow speed and fast speed pushbutton switches jointly, the slow speed or fast speed contactors will be energized to provide for continuous operation of said motor at slow speed or fast speed, by virtue of a maintaining circuit established by said limit switch, exclusive of said pushbutton switches, and said mixing machine when moved to dumping position being adapted to effect opening of said limit switch, to insure interruption of said last mentioned maintaining circuit.

7. In combination, an electric driving motor, a plurality of electromagnetic means operable selectively to effect connection of said motor to a source of current supply to provide for either slow speed operation or fast speed operation thereof, manually operable switching means for selectviely controlling energization of said electromagnetically operable connecting means, electrical interlocking means including an electromagnetically operable relay having contact parts respectively interposed between each of said connecting means and said manually operable switching means to require connection of said motor to said source for slow speed operation thereof prior to connection thereof to said source for fast speed operation in each instance, said electromagnetically operable relay also coacting with said manually operable switching means to insure complete disconnection of said motor from said source as an incident to changing from fast speed operation to slow speed operation thereof, said manually operable switching means including a pushbutton switch having a pair of contactors adapted when depressed to bridge their cooperating contacts in a predetermined sequence and to disengage their cooperating contacts in reverse sequence upon manual release of said pushbutton, said contactor first to bridge its cooperating contacts being initially incapable of effecting any control of said connecting means, but the same being adapted to maintain the control effected by the contactor last to bridge its cooperating contacts pending complete manual release of said bushbutton.

8. In combination, an electric driving motor, a plurality of electromagnetic means operable selectively to effect connection of said motor to a source of current supply to provide for either slow speed operation or fast speed operation thereof, manually operable switching means for selectively controlling energization of said electromagnetically operable connecting means, electrical interlocking means including an electromagnetically operable relay having contact parts respectively interposed between each of said connecting means and said manually operable switching means to require connection of said motor to said source for slow speed operation thereof prior to connection thereof to said source for fast speed operation in each instance, said electromagnetically operable relay also acting to insure complete disconnection of said motor from said source as an incident to changing from fast speed operation to slow speed operation thereof, a limit switch normally biased to closed position, means for moving said limit switch to open position under given conditions, said limit switch when closed acting to maintain given circuit connections for said motor independently of that portion of the manually operable switching means whose operation was required to effect completion of such circuit connections, and said manually operable switching means including a normally closed pushbutton switch electrically connected in series with said limit switch and depressible at will to render the latter ineffective for maintaining said given circuit connections.

9. In combination, an electric motor, a plurality of electromagnetic switches operable selectively to effect connection of said motor to a source of current supply to provide for either slow speed operation or fast speed operation thereof, manually operable switching means of the pushbutton type for selectively controlling energization of said electromagnetically operable connecting means, said manually operable switching means including a pushbuttom switch having a pair of contactors adapted to bridge their cooperating contacts in a predetermined sequence and to disengage their cooperating contacts in reverse sequence upon manual release of said pushbutton switch, the contactor first to bridge its cooperating contacts being initially incapable of effecting any control of said electromagnetically operable connecting means, but the same being adapted to maintain the control effected by the contactor last to bridge its cooperating contacts pending complete manual release of said pushbutton switch.

RICHARD B. HUNTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Mahnke Jan. 9, 1940 Number 

